EXFO FTB-500 (Window XP) - Manual (Page 124)

Using the Optional Built-In Power Meter and VFL
114 FTB-500
Setting Thresholds and Correction Factors
4. Tap Edit.
5. Modify the thresholds or correction factor for the selected wavelength.
6. Tap OK to close the dialog box and confirm the new values, then tap
OK to exit the window.